[Gasification] back to gasification
Florian Nagel
flopana77 at gmail.com
Thu Jun 2 11:36:16 CDT 2011
Hi James
You are absolutely right regarding the control valves. Nevertheless there
are research groups out there studying GT CC systems where the function of
the control valve is transferred to the valves controling the oxidant flow
into the gasifier and therefore the outflow of the producer gas, which is in
turn the fuel gas flow to the GT. If you can get such a system to work
properly (which in the end is a control headache due to the long reaction
times of the entire system
), you wouldnt need to cool the fuel gas down
before feeding it to the GT.
There is no doubt that methane is a better fuel for combustion engines as
you said. The reasons are manyfold and make absolute sense if you look a
little bit into the thermodynamics. Hydrogen may back-fire during the intake
phase, it may ignite during compression and thus create uncontrolled
pressure peaks, harming the engine on the one hand and requiring early
ignition points and lower compression ratios on the other hand. The latter
reduce the efficiency of combustion engine to a large extent. In addition
there is a serious water condensation issue on the ignition sparks during
cold starts (which is not that important for stationary working generator
engines..). Further, the volumetric energy content of hydrogen is around 3.5
times lower than that of methane, which leads to the lower power output when
operating a combustion engine with hydrogen instead of methane. You simply
dont get a lot of fuel into your cylinder.
Nevertheless, when we talk about power plant systems, we have to look at the
entire system and not only a part of it. Methanation is a process with a
certain conversion efficieny (typically 65%), which, when introduced into
the system, has to be compensated by efficiency benefits in the conversion
steps downstream (gas engine). Despite all the above mentioned drawbacks of
hydrogen as fuel and thus advantages of methane, this is hardly possible as
can be seen when looking at typical efficiency numbers. I think it makes a
lot more sense to look for gasification technologies that produce
methane-rich fuel gases and to burn this gas directly, rather than
introducing a methanation step. As Jan mentioned, steam gasification at
medium temperatures is a candidate. Further, updraft gasifiers typically
yield very high methane contents in the producer gas and so on
(http://e-collection.library.ethz.ch/view/eth:41553 , Page 21 and following
as well as Page 241 and following). Unfortunately, this possibility of
system optimisation (choosing the right components to minimize process
complexity and maximise system efficiency) is often overlooked.
Cheers
Florian
PS: Going very well, Jan. Didn't see you on Skype for a while. We should
definitely chat any time soon
cheers
From: gasification-bounces at lists.bioenergylists.org
[mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Jim
Leach
Sent: Wednesday, June 01, 2011 18:34
To: 'Discussion of biomass pyrolysis and gasification'
Subject: Re: [Gasification] back to gasification
Thanks again Florian,
I do have a couple of comments. You still have to cool the product gas down
for the gas turbine, not because of the turbine, but because of the gas
control valves. They have temperature limits that cannot be exceeded,
typically about 60C. Also, there is an energy benefit to methanation for
application to engines. The benefit is that converting the H2 to CH4 will
allow engines with higher BMEPs to be applied, and that means higher
efficiency, and greater output for the same engine frame size.
Best Regards,
JAMES T. LEACH, P.E.
President
DANA TECHNOLOGIES, INC.
32242 Paseo Adelanto, Suite D
San Juan Capistrano, CA 92675
Ph 949-496-6516
Fx 949-496-8133
Mobile 949-933-6518
_____
From: gasification-bounces at lists.bioenergylists.org
[mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Florian
Nagel
Sent: Wednesday, June 01, 2011 4:07 PM
To: 'Discussion of biomass pyrolysis and gasification'
Subject: Re: [Gasification] back to gasification
Hi James
Regarding gas engines, you are right that cooling is a must from a
thermodynamical perspective. Regarding gas turbines, a hot gas cleaning
process would be very nice to have (excuse me mentioning gas turbines in the
last sentence of the last comment
clearly doesnt belong there
) because the
turbines have the potential to stand high combustion temperatures. The
according exhaust gas would be in turn very hot, which makes the use of this
heat possible in a bottoming cycle. So, looking at a gasturbine combined
cycle, high fuel gas temperature does make sense if you adjust the
combustion temperature in a way that the gas turbine stands it and if you
use the exhaust heat. However, this requires a hot gas cleaning process. At
PSI, we operated high-temperature fuel cell with producer gas that was
cleaned in a hot gas cleaning system where the gas temperature never dropped
below 500C. Thus, there are ways to remove tars, etc. at high temperature
(Catalytic partial oxidation or high-temperature reforming steps). Anyways,
I wouldnt go so far and say that this technology is readily available ;o)
In any case, methanation is a great way to convert woody biomass into a more
usable and storable form but I dont quite see it in combination with gas
engines. Just to expensive and without real efficiency benefit if you aim at
electricity as end product.
Cheers
Florian
From: gasification-bounces at lists.bioenergylists.org
[mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Jim
Leach
Sent: Wednesday, June 01, 2011 17:18
To: 'Discussion of biomass pyrolysis and gasification'
Subject: Re: [Gasification] back to gasification
Thanks Florian,
If one wants to burn the product gas in an engine or a gas turbine you have
to cool and clean the gas anyway. So dropping the temperature would be a
part of the tar removal process and would occur anyway. Adding water is not
good because the product gas must be well below the dew point for the
combustion device. So it you put it in for methanation, you will have to
take it out later. But what I was interested in was simply converting the H2
to CH4, because engines (including GT's) don't really like H2 (it burns too
fast). Reciprocating engines in particular, would much prefer a steady diet
of CH4. But I think I understand from your answer is that it is not worth
it. Unfortunately, an answer I was expecting.
JAMES T. LEACH, P.E.
President
DANA TECHNOLOGIES, INC.
32242 Paseo Adelanto, Suite D
San Juan Capistrano, CA 92675
Ph 949-496-6516
Fx 949-496-8133
Mobile 949-933-6518
_____
From: gasification-bounces at lists.bioenergylists.org
[mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Florian
Nagel
Sent: Wednesday, June 01, 2011 2:52 PM
To: 'Discussion of biomass pyrolysis and gasification'
Subject: Re: [Gasification] back to gasification
Hi James
I cant comment on the cost of the methanation step but I can comment on your
idea regarding a methanation step as fuel upgrade in a gasification- and gas
engine-based power plant. I did my thesis together with Jan at PSI working
on the combination of high-temperature fuel cells with woody biomass
gasifiers: http://e-collection.library.ethz.ch/view/eth:41553 . Hi Jan, I m
still on that list as you see :D
Methanation is an exothermic process that yields the highest methane
concentration in the product gas when kept around 400C process temperature.
Hence, you ll first have to cool your syngas down to 400C. Depending on your
gasifier type and syngas composition, you might get into carbon deposition
problems (Boudouard reaction for example where 2 CO molecules decompose into
carbon and carbon dioxide). You can overcome these problems by injecting
steam into your syngas (which will cool it down at the same time..) which
you will also need to increase your hydrogen atom content in a way that
allows methanation. Then you can take it from there and produce methane.
Problem I see is that by introducing water into your fuel gas, you already
lower its heating value. This results in a lower combustion temperature in
your gas engine. Gas engines are limited by the Carnot efficiency rule that
clearly states that the efficiency of a combustion engine increases with the
difference between the temperature of the hot compressed combusted gas and
the temperature of the expanded exhaust gas. Hence, the efficiency of a
combustion engine running on humidized syngas should definitely be lower
than running on unhumidified syngas. Next problem is, during the methanation
you have to cool the reactor. Thus you are again reducing the energy content
of your syngas or by that time synthetic methane (relative to the energy
content of the initial feedstock). The energy you extract from the
methanation process is in form of low-temperature heat (400C) which you can
hardly use economically to produce electricity with a steam cycle. Once you
have your synthetic methane gas mixture, you ll have to reduce the high
water content of it to not run into above mentioned efficiency issues of the
combustion engine. This can only be done by cooling the gas close to ambient
temperature were the water simply condenses. Another point in the process
were you extract energy at very very low temperature level. I would consider
this energy as a complete loss. From there you can use the dried, cold
synthetic methane in your engine and produce electricity.
To put it in numbers: Good gasification-gas engine plants reach efficiencies
around 25 to 30% without bottoming-cycle (steam cycle to use exhaust heat).
The methanation process has an efficiency around 65%. Together with a very
high combustion engine efficiency of 42.5%, you end up with a maximum
efficiency of a gasification-methanation-gas engine scheme of around 27.5%.
However, with considerably higher equipment cost. I definitely recommend not
to use a methanation step as fuel upgrading step but to use the syngas
directly in your engine. In any case, the world totally changes if you aim
at using high-temperature fuel cells, gas turbines or if you want to make
the wood energy transportable and storable. The latter was the idea of the
PSI methanation project given Switzerlands dependence on foreign gas
imports.
Cheers
Florian
From: gasification-bounces at lists.bioenergylists.org
[mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Jim
Leach
Sent: Wednesday, June 01, 2011 15:51
To: 'Discussion of biomass pyrolysis and gasification'
Subject: Re: [Gasification] back to gasification
Jan,
I am curious what method you selected for tar removal. Also, was the
methanation step expensive? The methane would make a better engine fuel
than the H2 and CO but I am concerned about the cost.
Best Regards,
JAMES T. LEACH, P.E.
President
DANA TECHNOLOGIES, INC.
32242 Paseo Adelanto, Suite D
San Juan Capistrano, CA 92675
Ph 949-496-6516
Fx 949-496-8133
Mobile 949-933-6518
_____
From: gasification-bounces at lists.bioenergylists.org
[mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Jan
Kopyscinski
Sent: Wednesday, June 01, 2011 1:13 PM
To: Discussion of biomass pyrolysis and gasification
Subject: Re: [Gasification] back to gasification
Hi Kevin,
I did my Phd thesis on this topic. You can find more information there:
http://e-collection.library.ethz.ch/view/eth:1059
or under www.bio-sng.com and www.biosng.com,
http://www.biofuelstp.eu/bio-sng.html and on other pages.
In a nut shell the process consits of:
1) low temperature steam gasification
2) gas cleaning (ash, tar, H2S, ...)
3) methanation = conversion of the syngas into methan (catalytic process,
mostly Nickelcatalyst)
CO + 3 H2 --> CH4 + H2O
CO + H2O --> H2 + CO2
If you use a different catalyst you can go for higher hydrocarbon such as
Fischer Tropsch Diesel, or Methanol, ....
4) Fuel upgrading = removal of H2O, CO2
We at the Paul Scherrer Institute in Switzerland (http://tpe.web.psi.ch/)
investigated this process from wood to BioSNG in two scales for more than
1000h.
Regards
Jan
-
Dr. sc. Jan Kopyscinski
Postdoctoral fellow
Department of Chemical and Petroleum Engineering
Schulich School of Engineering
University of Calgary
2500 University Drive NW
Calgary, Alberta, Canada T2N 1N4
Email: jan.kopyscinski at ucalgary.ca
Phone: 001 403 2109575
_____
Von: Kevin <kchisholm at ca.inter.net>
Gesendet: May 31, 2011 5:02:24 PM
An: "Discussion of biomass pyrolysis and gasification"
<gasification at lists.bioenergylists.org>
Betreff: Re: [Gasification] back to gasification
Dear Jan
Very interesting!!
What steam temperature and pressure is required to gasify wood?
Once one has such gas, what sort processing is required to convert it to
CH4? (That is, what temperatures, pressures, catalysts, etc)
Is there any way this can be done on a small scale?
Is there any way this process can be modified to produce methanol on a small
scale? If so, this would be awesome... it would then yield a very portable
liquid fuel.
Thanks!
Kevin
----- Original Message -----
From: Jan Kopyscinski <mailto:jan.kopy at web.de>
To: Discussion of biomass pyrolysis and gasification
<mailto:gasification at lists.bioenergylists.org>
Sent: Tuesday, May 31, 2011 11:30 AM
Subject: Re: [Gasification] back to gasification
Hi,
First of all, there are at least two different types of biofuel:
First Generation: agricultural feedstock, which is converted by means of
biochemical processes (i.e., digestion) --> Biogas
Second Generation: woody biomass that is converted via thermochemical
converiosn into a producer or so-calles syngas (Gasification).
Thus, if your goal is to produce Methan or Natural Gas substite for a gas
engine or transportation fuel you have different options. But you need to
know what is your feedstock (dry , wet, digestable or not digestable such as
wood):
If you have a rather dry feedstock you can go for steam gasifiaction (no
air, means no Nitrogen). The produced syngas you can catalytilcally convert
to CH4, CO2 and H2O. Prior to the methanation process you need to remove the
sulphur since it is deactivating your catalyts. H2O and CO2 can then be
removed. This process has been investiaget by the Paul Scherrer Institiute
in Switzerland (www.psi.ch and www.bio-sng.com).
Removal of nitrogen is too expensive, thus you should avoid feeding it into
your process. 2 vol% to max 5vol% N2 in the methan rich gas is acceptable.
Regards,
Jan
_____
Von: "Pannirselvam P.V" <pannirbr at gmail.com>
Gesendet: May 31, 2011 12:46:54 PM
An: "Discussion of biomass pyrolysis and gasification"
<gasification at lists.bioenergylists.org>
Betreff: Re: [Gasification] back to gasification
Dear A.D Karve
One of the project we have been studying is based on the
IGT,Instuite Gas technology patented process called Biotherm , in which
the wood gas or syngqs can be passed into the biodigestor, in which CO
and Hydrogen can be converted into methane ; the NOX .COX, SOX removed
via simple known wet or dry process using activated charcoal and lime ;
the methane is then compressed.The N can be removed as ammonia,as this can
be very toxic to bio methane bacteria; Syngas obtained via pyrogas can
reduce this N2 problem and complexity.Thus pyrogas technology has more
potential than wood gas technology
we are studying how to make this complex process into simple innovative
process to make possible charcoal and methane economy which is practiced
in the developed country in big scale can be made possible in developing
village level technology too in small scale ,The project is yet in design
stage to reduce CO2 to use as liquid fertilizer too increasing the
calorific valued the compressed biogas.
Yours truely
Pannirselvam
On Mon, May 30, 2011 at 11:01 PM, Anand Karve <adkarve at gmail.com> wrote:
Dear List,
We are already using, in India, wood gas made from agricultural waste
to run stationary internal combustion engines. But, for using it as
automobile fuel, it would have to be filled into cylinders, for which
the nitrogen in the wood gas would have to be removed in order to
reduce its bulk and to increase its calorfiic value. Does anybody have
a suggestion as to how this can be achieved?
Yours
A.D.Karve
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